every time that my 2007 macbook with lion goes to sleep, either manually (closing the lid) or timing out, i have to restart my computer to connect to the wireless network. It fails to detect any networks at all until I restart, then it connects to my default network no problem. What can I do?

Expand the Solution section under Symptom: The network connection drops unexpectedly and follow the steps listed under Symptom: After restarting or waking from sleep, my computer might not connect to the Internet.

Just make sure you write down all the passwords for the networks you want to keep as deleting the keys in keychain will permanently remove them.